CVE-2026-33753

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 91% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 7.5Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates, an attacker can append a spoofed certificate matching the target common_name and Extended Key Usage (EKU) requirements. This tricks the library into verifying these authorization rules against the forged certificate while validating the cryptographic signature against an actual trusted TSA (such as FreeTSA), thereby bypassing the intended TSA authorization pinning entirely. This vulnerability is fixed in 1.0.6.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
50
EG Risk 50/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation40% × 40%
Automatability0% × 15%
EPSS PROB
0.2%
EPSS %ILE
9th
KEV
Not listed

Published

April 8, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated Jun 15, 2026
🔬 Proof of concept available. Patch available. Sources: github.
githubMentions a patch (unverified)🟡 PoC Available

Improper Certificate Validation in rfc3161-client · Advisory · trailofbits/rfc3161-client · GitHub

https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
rfc3161-client0.0.2 ... 1.0.5 (12 versions)
  • every version up to 1.0.6: fixed in 1.0.6
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 27× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 181 total refreshes for this CVE.

  1. 2026-10-10 21:47 UTCOSV refresh
  2. 2026-10-10 20:00 UTCEPSS rescore
  3. 2026-10-09 20:07 UTCEPSS rescore
  4. 2026-10-08 17:12 UTCEPSS rescore
  5. 2026-10-07 23:47 UTCEPSS rescore
  6. 2026-10-06 15:17 UTCEPSS rescore
  7. 2026-10-05 17:42 UTCEPSS rescore
  8. 2026-10-04 23:22 UTCEPSS rescore
  9. 2026-10-03 14:25 UTCEPSS rescore
  10. 2026-10-01 19:49 UTCEPSS rescore
  11. 2026-09-30 15:03 UTCEPSS rescore
  12. 2026-09-28 13:51 UTCEPSS rescore
  13. 2026-09-27 13:48 UTCEPSS rescore
  14. 2026-09-26 15:58 UTCEPSS rescore
  15. 2026-09-26 00:26 UTCEPSS rescore
  16. 2026-09-21 09:49 UTCOSV refresh
  17. 2026-09-20 20:15 UTCEPSS rescore
  18. 2026-09-18 19:28 UTCEPSS rescore
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  20. 2026-09-17 19:30 UTCEPSS rescore
  21. 2026-09-16 14:08 UTCEPSS rescore
  22. 2026-09-16 05:15 UTCEPSS rescore
  23. 2026-09-15 03:11 UTCEPSS rescore
  24. 2026-09-13 16:47 UTCEPSS rescore
  25. 2026-09-12 15:01 UTCEPSS rescore
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  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 09:37 UTCEPSS rescore
  3. 2026-09-10 09:34 UTCEPSS rescore
  4. 2026-09-08 22:00 UTCEPSS rescore
  5. 2026-09-07 16:01 UTCEPSS rescore
  6. 2026-09-06 13:47 UTCEPSS rescore
  7. 2026-09-04 05:06 UTCEPSS rescore
  8. 2026-09-02 14:11 UTCEPSS rescore
  9. 2026-09-02 07:44 UTCOSV refresh
  10. 2026-09-01 13:53 UTCEPSS rescore
  11. 2026-09-01 04:39 UTCEPSS rescore
  12. 2026-09-01 04:39 UTCEPSS rescore
  13. 2026-08-30 19:17 UTCEPSS rescore
  14. 2026-08-30 01:22 UTCEPSS rescore
  15. 2026-08-28 21:41 UTCEPSS rescore
  16. 2026-08-27 14:25 UTCEPSS rescore
  17. 2026-08-26 14:46 UTCEPSS rescore
  18. 2026-08-25 13:49 UTCEPSS rescore
  19. 2026-08-24 14:17 UTCEPSS rescore
  20. 2026-08-21 23:49 UTCEPSS rescore
  21. 2026-08-20 22:55 UTCEPSS rescore
  22. 2026-08-20 22:55 UTCEPSS rescore
  23. 2026-08-19 17:03 UTCEPSS rescore
  24. 2026-08-18 13:48 UTCEPSS rescore
  25. 2026-08-17 13:47 UTCEPSS rescore
  26. 2026-08-16 14:56 UTCEPSS rescore
  27. 2026-08-16 07:20 UTCEG score recompute
  28. 2026-08-16 02:14 UTCEPSS rescore
  29. 2026-08-15 01:30 UTCEPSS rescore
  30. 2026-08-14 05:16 UTCEG score recompute
  31. 2026-08-13 22:00 UTCEPSS rescore
  32. 2026-08-12 19:32 UTCEG score recompute
  33. 2026-08-12 13:50 UTCEPSS rescore
  34. 2026-08-11 19:46 UTCEG score recompute
  35. 2026-08-11 03:07 UTCEG score recompute
  36. 2026-08-11 00:00 UTCEPSS rescore
  37. 2026-08-09 16:27 UTCEG score recompute
  38. 2026-08-09 13:46 UTCEPSS rescore
  39. 2026-08-08 02:23 UTCEG score recompute
  40. 2026-08-07 14:41 UTCEG score recompute
  41. 2026-08-06 13:46 UTCEPSS rescore
  42. 2026-08-05 23:51 UTCEG score recompute
  43. 2026-08-05 19:17 UTCEPSS rescore
  44. 2026-08-04 15:10 UTCEPSS rescore
  45. 2026-08-04 10:38 UTCEPSS rescore
  46. 2026-08-03 22:08 UTCEG score recompute
  47. 2026-08-03 10:36 UTCEPSS rescore
  48. 2026-08-02 14:06 UTCEG score recompute
  49. 2026-08-02 02:27 UTCEPSS rescore
  50. 2026-08-01 04:16 UTCEPSS rescore
  51. 2026-07-30 16:28 UTCEPSS rescore
  52. 2026-07-30 01:30 UTCEPSS rescore
  53. 2026-07-27 14:13 UTCEPSS rescore
  54. 2026-07-26 14:54 UTCEPSS rescore
  55. 2026-07-26 14:54 UTCEPSS rescore
  56. 2026-07-26 08:46 UTCEG score recompute▲ 1.30
  57. 2026-07-25 14:18 UTCEPSS rescore
  58. 2026-07-25 14:18 UTCEPSS rescore
  59. 2026-07-24 22:12 UTCNVD updateCVSS v3 → 7.5 · severity → HIGH
  60. 2026-07-24 14:17 UTCEPSS rescore
  61. 2026-07-24 14:17 UTCEPSS rescore
  62. 2026-07-23 14:18 UTCEPSS rescore
  63. 2026-07-23 14:18 UTCEPSS rescore
  64. 2026-07-23 03:09 UTCEG score recompute
  65. 2026-07-22 14:08 UTCEPSS rescore
  66. 2026-07-21 15:24 UTCEPSS rescore
  67. 2026-07-20 22:02 UTCOSV refresh
  68. 2026-07-20 17:08 UTCEPSS rescore
  69. 2026-07-19 14:31 UTCEPSS rescore
  70. 2026-07-19 02:29 UTCEPSS rescore
  71. 2026-07-18 10:04 UTCEPSS rescore
  72. 2026-07-16 17:03 UTCEPSS rescore
  73. 2026-07-15 16:57 UTCEPSS rescore
  74. 2026-07-15 16:57 UTCEPSS rescore
  75. 2026-07-15 02:00 UTCEPSS rescore

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PyPI:rfc3161-client

Frequently asked(5)

What is CVE-2026-33753?
CVE-2026-33753 is a high vulnerability published on April 8, 2026. rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw…
When was CVE-2026-33753 disclosed?
CVE-2026-33753 was first published on April 8, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33753 actively exploited?
CVE-2026-33753 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (9th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-33753?
CVE-2026-33753 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-33753?
A fix for CVE-2026-33753 is available: update to the fixed version the vendor names in its advisory.

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